My son is studying unit conversions in school and as a family we were discussing how you can’t use the same technique (multiplication) when converting between Celsius and Fahrenheit. Out of this conversation came a new temperature scale, Tarenheit (rhymes with Fahrenheit).

Tarenheit is exactly 32^{°} less than Fahrenheit.

Fahrenheit | Tarenheit |
---|---|

32^{°} |
0^{°} |

100^{°} |
68^{°} |

212^{°} |
180^{°} |

## The Problem with Converting Between Celsius and Fahrenheit

Typically when converting between units, both units are equivalent at 0.

For example:

0 inches = 0 cm

0 kg = 0 lbs

etc.

Unfortunately, this does not hold true for Celsius and Fahrenheit

0^{°} C does NOT equal 0^{°} F

Since Celsius and Fahrenheit are not equivalent at zero, you can not simply multiply to do the conversion.

Instead to get Fahrenheit from Celsius, the formula is:

(c * 9/5) + 32

and to get Celsius from Fahrenheit, the formula is:

(f – 32) * (5/9)

## Introducing Tarenheit

Since Tarenheit is 32^{°} less than Fahrenheit, Tarenheit *is* equivalent to Celsius at zero.

We can multiply Tarenheit by 5/9 to get Celsius

or we can multiply Celsius by 9/5 to get Tarenheit.

### A Stepping Stone

Now, we can go from Celsius to Tarenheit with multiplication – and then from Tarenheit to Fahrenheit by adding 32.

Likewise, we can go from Fahrenheit to Tarenheit by subtracting 32, then from Tarenheit to Celsius with multiplication.

We are doing all the same steps but now we can do it one step at a time.

Perhaps you don’t need this stepping stone but for those of us (or maybe just me) who find handling the offset *and* multiplication in one step cumbersome, breaking this into two steps may be helpful.

## Why “Tarenheit”?

Tarenheit is a combination of the words tare (*to adjust (a scale on which an empty container has been placed) so as to reduce the displayed weight to zero*, see Merriam Webster definition 3) and Fahrenheit.

Thank you to my wife Kate for this clever word play.

Mickey Mellen says

Tarenheit is a fascinating solution. I prefer the rough math of “double + 30” for c –> f and the reverse for going from f –> c. In most cases, it gets you within a couple of degrees, which is good enough.

Is it 30 c right now? Double (60) + 30, and it’s roughly 90 f. It’s a good shortcut.

Sal Ferrarello says

Strong agree that double + 30 is great (and quick) estimate for Celsius to Fahrenheit conversion.